Common (Translated Scientific) Name: Switchgrass - Eastern Gamagrass Grassland Alliance

Colloquial Name: Southern Switchgrass - Eastern Gamagrass Grassland

Hierarchy Level:  Alliance

Type Concept: This alliance includes wet-mesic grasslands of the blackland and coastal prairie regions extending from the Gulf Coastal Plain of Texas and Louisiana north into Oklahoma. These grasslands are typically dominated or codominated by Panicum virgatum and/or Tripsacum dactyloides. Associated grasses and sedges include Panicum hemitomon, Spartina patens, Carex sp., Scleria sp., Rhynchospora sp., and Fimbristylis sp. Important forbs may include Pluchea odorata, Symphyotrichum lateriflorum, Physostegia pulchella, Acacia angustissima var. hirta, Symphyotrichum ericoides, Bifora americana, Stenaria nigricans, Helianthus maximiliani, Ratibida columnifera, Rudbeckia hirta, and Ruellia humilis. This alliance occurs on poorly drained or subirrigated areas interdigitated within a matrix of slightly higher upland prairies dominated or codominated by Schizachyrium scoparium. These low areas include broad low flats, drainage swales, small shallow basins, riparian areas, and inter-mound areas in prairies with mound-intermound microtopography. Soils include Alfisols, Mollisols, and Vertisols. Gilgai microtopography, with circular depressions and ridges, is characteristic of this community where it occurs over Vertisols. Often, the microtopographic low areas occupied by this community (small shallow basins, small drainage swales, and intermound areas) are too small to have been assigned separate soil types. They may be found as inclusions in areas mapped as hydric or non-hydric soils. Fire and native grazing likely played a role historically in maintaining this vegetation.

Diagnostic Characteristics: This alliance is characterized by the dominance or codominance of Panicum virgatum and Tripsacum dactyloides in wet-mesic areas of the Blackland and Coastal Prairie regions of Texas and Louisiana extending peripherally into Oklahoma.

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: Extremely few examples of wet coastal prairie remain and additional plot data and analyses are needed. This alliance once occupied hundreds of thousands of acres on the Prairie Terraces of southwestern Louisiana, but few, if any, intact examples remain (MacRoberts and MacRoberts 1997b). Also once extensive from the Texas coast to the Red River, it now occurs as isolated remnants, often surrounded by cropland. Eastern gammagrass-dominated areas are the most endangered grasslands in Texas (D. Diamond pers. comm.) and are very restricted and subject to grazing pressures. Most areas have been plowed. Without appropriate disturbance regimes, these grasslands rapidly deteriorate and may become invaded by woody species. In the northern Blackland Prairie region of Texas, composition of this alliance can vary considerably as a result of management history. In deteriorated examples, Panicum virgatum may be replaced in importance by Helianthus maximiliani, Symphyotrichum ericoides, and others (J. Eidson pers. comm.). Further classification work is needed to fully resolve the differences and similarities between the associations in this alliance.

Similar NVC Types: No Data Available

note: No Data Available